Optical fibers have been widely used in optical communications for propagating light over long distances. Light propagates through the core region of optical fibers and these core regions can be as small as a few microns in diameter. Although the fibers can be fabricated in lengths of many kilometers, multiple optical fibers must be joined together or coupled for transmission across greater distances. One critical consideration during coupling is accurate alignment of fibers to avoid loss of light transmitted through the coupling.
Further, as optical devices continue to shrink, and integration of multiple devices on a single chip becomes more popular, fiber positioning elements become more valuable. Many photonic applications require precision alignment of one- and two-dimensional arrays of optical fibers to optical elements that emit or receive light. Examples of such optical elements include, but are not limited to, lenses, detectors, laser sources and other optical fibers. Particular examples of applications that require precision alignment of arrays of optical fibers to optical elements include two-dimensional fiber array connectors in optical data or communication applications, two-dimensional fiber-lens arrays for three-dimensional optical cross connection switches, and two dimensional fiber-detector arrays for broadcast and network interconnection schemes.
A challenge in assembly of two-dimensional optical element arrays is precision positioning of each fiber during alignment and attachment processes. Typical multimode applications require each fiber to be placed on a two-dimensional array with a positional accuracy of less than 5 microns. Typical single-mode fiber alignment applications (to other fibers or optical elements such as lenses or laser sources) require lateral positional accuracy of less than 1-2 microns, while other applications require sub-micron positional accuracy.
Many devices and methods have been provided for positioning fibers in two-dimensional arrays, including etched silicon alignment structures, alignment blocks with holes to guide fibers, and stacked structures that form fiber guides. In each of these devices and methods, the alignment structures provide relatively “hard” and inflexible surfaces for fiber alignment, leading to small misalignments in cases where the physical size of the optical element varies slightly from element to element across the array.
Numerous articles and methods have been devised in the prior art to provide planar fiber positioning elements which allow for efficient coupling of optical fibers to substrates. However, the need for critical alignment tolerances has resulted in a high degree of complexity and cost for these devices. Further, the need for critical alignment tolerances has resulted in precision devices that are difficult to manufacture in an automated manner. One such device is a multi-fiber ferrule connector, such as a MT-type ferrule connector, as shown in FIGS. 1 and 2. MT-type ferrules are expensive, difficult to manufacture and, during assembly, require the optical fibers to be threaded through small bore holes with extremely tight tolerances. Threading fibers into bores with such tight tolerances is difficult to automate.
Consequently, a need exists for a sub-assembly for simplifying the fiber presentation that maintains accurate positioning of the fibers in an array, and enables automated assembly.